Light emitting device and production method and use thereof

ABSTRACT

A light emitting device includes an epitaxial structure and first and second electrodes on a side of the epitaxial structure. The epitaxial structure includes a first-type semiconductor layer, an active layer, and a second-type semiconductor layer. The active layer is disposed between the first-type semiconductor layer and the second-type semiconductor layer. The first electrode is disposed on the epitaxial structure to be electrically connected with the first-type semiconductor layer. The second electrode is disposed on the epitaxial structure to be electrically connected with the second-type semiconductor layer. The second electrode is in ohmic contact with a second-type window sublayer of the second-type semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 17/084,223, filed on Oct. 29, 2020, which is abypass continuation-in-part application of International Application No.PCT/CN2019/076136 filed on Feb. 26, 2019, which claims priority ofChinese Patent Application No. 201810411333.1, filed on May 2, 2018. Theentire content of each of the international and Chinese patentapplications is incorporated herein by reference.

FIELD

The disclosure relates to a light emitting device and a productionmethod and use thereof, and more particularly to a flip-chip lightemitting device and a production method and use thereof.

BACKGROUND

Advantages of flip-chip light emitting diodes (LEDs) reside in that wirebonding is not required, that electrodes can be arranged not to blocklight emission, and that excellent heat dissipation can be achieved. Dueto such advantages, light emitting efficiency of these diodes can beenhanced. For instance, FIG. 1 shows a conventional flip-chip LED thatis AlGaInP-based, and that includes a transparent substrate 101, asemiconductor structure (normally including a first-type semiconductorlayer 111, an active layer 112, and a second-type semiconductor layer113), and a transparent bonding layer 120 interconnecting thetransparent substrate 101 and the semiconductor structure. The flip-chipLED shown in FIG. 1 further includes first-type and second-type ohmiccontact electrodes 121, 122 (which may be p-type and n-type) that aredisposed on the semiconductor structure opposite to the transparentsubstrate 101 and on the same side of the semiconductor structure. Forpackaging the flip-chip LED shown in FIG. 1 , die bonding is applied tothe electrodes 121, 122 for electrical connection.

CN 101897048 A discloses a thin flip-chip light emitting device that isAlGaInP-based, as well as a production method of such device.Specifically, n-type and p-type electrodes are formed on the same sideof a semiconductor structure, and the semiconductor structure with suchelectrodes is connected to amount by way of metallic bonding.Subsequently, a growth substrate, on which the semiconductor structureis formed, is removed.

Moreover, CN 107681034 A discloses a flip-chip micro LED and aproduction method thereof. To be exact, n-type and p-type electrodes areformed on a side of a semiconductor structure, and the semiconductorstructure with such electrodes is bonded to a support substrate,followed by removing a growth substrate on which the semiconductorstructure is formed.

Since the aforesaid two Chinese patents both require the semiconductorstructure to be connected to the substrate or amount byway of bondingfor subsequently removing the growth substrate, the bonding processmight cause the LED to be damaged, hence reducing the production yield.

SUMMARY

Therefore, an object of the disclosure is to provide a light emittingdevice, a production method thereof, and a light emitting apparatusincluding such device which can alleviate at least one of the drawbacksof the prior art.

According to a first aspect of the disclosure, the light emitting deviceincludes an epitaxial structure, a first electrode, and a secondelectrode.

The epitaxial structure includes a first-type semiconductor layer, anactive layer, and a second-type semiconductor layer. The second-typesemiconductor layer has a second-type cladding sublayer and asecond-type window sublayer. The active layer is made from aluminumgallium indium phosphide (AlGaInP) and is disposed on the second-typesemiconductor layer. The first-type semiconductor layer is disposed onthe active layer opposite to the second-type semiconductor layer.

The first electrode is disposed on an electrode placement side of theepitaxial structure, so that the first electrode is electricallyconnected with the first-type semiconductor layer.

The second electrode is disposed on the electrode placement side of theepitaxial structure, so that the second electrode is electricallyconnected with the second-type semiconductor layer. The second electrodeis in ohmic contact with the second-type window sublayer.

According to a second aspect of the disclosure, the light emittingapparatus includes at least one light emitting device as describedabove.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the disclosure will become apparent inthe following detailed description of the embodiment (s) with referenceto the accompanying drawings, of which:

FIG. 1 is a schematic sectional view illustrating a conventionalflip-chip light emitting diode;

FIG. 2 is a schematic sectional view illustrating an epitaxial structurefor a flip-chip light emitting device formed on a growth substrate andincluding an AlGaInP-based current spreading layer;

FIG. 3 is a schematic sectional view illustrating an epitaxial structurefor a flip-chip light emitting device formed on a growth substrate andincluding an AlGaAs-based current spreading layer;

FIG. 4 is a flow chart showing steps S1 to S3 of a first embodiment of amethod for producing a flip-chip light emitting device according to thepresent disclosure;

FIG. 5 is a flow chart showing substeps S11 to S13 of step S1 of thefirst embodiment of the method;

FIGS. 6 to 11 are schematic sectional views illustrating steps S1 to S3of the first embodiment of the method; and

FIG. 12 is a schematic sectional view illustrating a flip-chip lightemitting device produced using a fifth embodiment of the method.

DETAILED DESCRIPTION

Before describing embodiments of a flip-chip light emitting device and aproduction method thereof according to the present disclosure in detail,experimental results obtained by the applicant are first described belowfor better understanding of the present disclosure.

Specifically, since a current spreading layer on a n-type or p-typesemiconductor layer of an epitaxial structure (i.e. a semiconductorstructure) for a flip-chip light emitting device greatly influences thelight emitting efficiency and production yield of such epitaxialstructure, the applicant prepared two epitaxial structures respectivelyincluding aluminum gallium indium phosphide (AlGaInP)-based and aluminumgallium arsenide (AlGaAs)-based current spreading layers, and conductedpreliminary experiments thereon. Referring to FIG. 2 , an epitaxialstructure for a flip-chip light emitting device was epitaxially grown ona growth substrate 200, and had an AlGaInP-based light emittingcomponent. The epitaxial structure included a buffer layer 201, an etchstop layer 202, a contact layer 203, an(Al_(0.6)Ga_(0.4))_(0.5)In_(0.5)P (AlGaInP-based) current spreadinglayer 204, an n-type layer 205, a multiple-quantum-well (MQW) activelayer 206, a p-type layer 207, and a window layer 208, which werearranged on the growth substrate 200 in such sequential order. However,during the epitaxial growth of the AlGaInP-based current spreading layer204, the temperature window was in a narrow range (±10° C.). Inaddition, due to the limitation to the incorporation efficiency of In,the growth rate became sensitive to the temperature. Thus, the growthrate, when reaching 7 Å/s, was at the limit, rendering the crystalgrowth hardly controllable.

Referring to FIG. 3 , an epitaxial structure for a flip-chip lightemitting device was epitaxially grown on a growth substrate 300 throughmetal organic chemical vapor deposition (MOCVD), and had anAlGaInP-based light emitting component. The epitaxial structure includeda n-GaAs buffer layer 301 (having a thickness of 0.2 μm), a GaInP etchstop layer 302 (having a thickness of 0.2 μm), an n-GaAs contact layer303 (having a thickness of 70 nm), an Al_(0.45)Ga_(0.55)As(AlGaAs-based) current spreading layer 304 (having a thickness of 3 μm),an n-AlInP n-type layer 305 (having a thickness of 0.3 μm), an MQWactive layer 306 (having a thickness of 0.2 μm and generally made from(Al_(0.5)Ga_(0.5))_(0.5)In_(0.5)P), a p-AlInP p-type layer 307 (having athickness of 0.3 μm), and a p-GaP window layer 308 (having a thicknessof 1.2 μm), which were arranged on the growth substrate 300 in suchsequential order. The wells and barriers of the MQW active layer 306were made from (Al_(y)Ga_(1-y))_(z)In_(1-z)P, where each of y and z islarger than 0 and smaller than 1. By adjusting the ratio of y to z, theepitaxial structure could be designed to emit light having a wavelengthof 560 nm to 650 nm (i.e. green light, yellow light, orange light, orred light). Specifically, the wells and barriers were made from(Al_(0.1)Ga_(0.9))_(0.5)In_(0.5)P and(Al_(0.65)Ga_(0.35))_(0.5)In_(0.5)P, respectively, such that theepitaxial structure could emit light having a wavelength of 620 nm to624 nm (i.e. red light). The n-AlInP n-type layer 305 and the p-AlInPp-type layer 307 provided electrons and holes, respectively. The windowlayer 308 served to spread electric currents on the p-type layer 307.The growth temperature of the Al_(0.45)Ga_(0.45)As current spreadinglayer 304 ranged from 650° C. to 710° C., and the growth time of suchlayer was 25 minutes. The metal-organic (MO) sources for the growth ofthe Al_(0.45)Ga_(0.45)As current spreading layer 304 were trimethylaluminum (TMAl), trimethyl gallium (TMGa), and AsH₃.

The epitaxial structure with the AlGaAs-based (Al_(0.45)Ga_(0.45)As)current spreading layer 304 shown in FIG. 3 had the following advantagesover the epitaxial structure with the AlGaInP-based((Al_(0.6)Ga_(0.4))_(0.5)In_(0.5)P) current spreading layer 204 shown inFIG. 2 . The temperature window for the growth of theAl_(0.45)Ga_(0.45)As current spreading layer 304 was 680±30° C. Comparedto the (Al_(0.6)Ga_(0.4))_(0.5)In_(0.5)P current spreading layer 204having the same thickness, the growth time for the Al_(0.45)Ga_(0.45)Ascurrent spreading layer 304 was shortened to 25 minutes, therebyreducing the time for epitaxially growing the epitaxial structure byabout 30%. During the epitaxial growth by MOCVD, the amount of PH₃consumption was greatly reduced, hence improving the safety and loweringthe production cost. If the epitaxial growth by MOCVD could employ asource more efficiently providing As, the production cost could befurther lowered.

Further, the applicant used the epitaxial structure with theAlGaAs-based (Al_(0.45)Ga_(0.45)As) current spreading layer 304 shown inFIG. 3 to produce a flip-chip red-light emitting device (not shown inthe drawings) using the following steps. A transparent dielectric layerwas disposed on the window layer 308 opposite to the p-type layer 307,and a mirror layer was formed on the transparent dielectric layeropposite to the window layer 308 through deposition, so as to form atotal reflection unit. A metallic bonding layer was formed on the mirrorlayer opposite to the dielectric layer through deposition. A permanentsubstrate was provided and was disposed on the metallic bonding layeropposite to the mirror layer, followed by conducting a high-temperatureand high-pressure bonding process to bond the epitaxial structure to thepermanent substrate. Subsequently, the growth substrate 300, the bufferlayer 301, and the etch stop layer 302 were removed through thinning andchemical etching to expose the contact layer 303. A first electrode wasformed on the exposed contact layer 303, and then a part of the exposedcontact layer 303 where the first electrode was not formed was subjectedto etching to expose the current spreading layer 304. The exposedcurrent spreading layer 304 was roughened to form a light exit surface.Aback electrode was formed on the permanent substrate opposite to themirror layer, such that the flip-chip red-light emitting device wasobtained.

The mirror layer may be made from a monolayer of gold or agold-containing alloy, or a multilayer of mirror material. The permanentsubstrate may be made from a common substrate material such as silicon,silicon nitride, etc. The first electrode and the back electrode may bemade from a common metallic material such as gold, platinum, nickel,chromium, germanium, and alloys thereof.

The flip-chip red-light emitting device was subjected to ananti-electrostatic discharge (anti-ESD) test. It was found that theanti-ESD4000V performance of the flip-chip red-light emitting device was25% better that of a flip-chip light emitting device produced in asimilar manner but using the epitaxial structure with the AlGaInP-basedcurrent spreading layer 204 shown in FIG. 2 , indicating that suchimproved device can satisfy the performance requirement at high voltage.

In addition, the applicant produced another flip-chip light emittingdevice (not shown in the drawings) using steps generally similar tothose described above for producing the flip-chip red-light emittingdevice, except that the AlGaAs-based current spreading layer applied wasa Al_(x)Ga_(1-x)As current spreading layer, where x is larger than 0 andless than 1. To be specific, x is a value not less than 0.45 and notgreater than 0.65, such as 0.55. If x is greater than 0.65, the currentspreading layer might undesirably increase voltage to higher than 0.23Vwhich is out of a suitable voltage range for a regular light emittingdevice. The flip-chip light emitting device thus produced was tested andhad anti-ESD performance which was 23% better that of the flip-chiplight emitting device produced in a similar manner but using theepitaxial structure with the AlGaInP-based current spreading layer 204shown in FIG. 2 .

Lastly, the applicant prepared an epitaxial structure (not shown in thedrawings) using steps generally similar to those described above forproducing the epitaxial structure shown in FIG. 3 , except that thecurrent spreading layer applied was an n-type doped current spreadinglayer. The doping concentration ranged from 1×10¹⁸ to 2×10¹⁸. To beexact, the doping concentration was 1.5×10¹⁸. During the epitaxialgrowth, the current spreading layer was subjected to doping with asilicon source. The doping concentration could be controlled byadjusting the flow rate of the silicon source. By virtue of n-typedoping, contact resistance between the current spreading layer and then-type layer or the MQW active layer could be reduced, such that theepitaxial structure could be prevented from overheating and powerconsumption.

Based on the aforesaid experimental results, the applicant conceived theflip-chip light emitting device and the production method thereofaccording to the present disclosure, which are now described.

Before the disclosure is described, it should be noted that whereconsidered appropriate, reference numerals or terminal portions ofreference numerals have been repeated among the figures to indicatecorresponding or analogous elements, which may optionally have similarcharacteristics.

Referring to FIG. 4 , a first embodiment of the production methodaccording to the present disclosure includes steps S1 to S3. Referringto FIG. 5 , step S1 includes substeps S11 to S13.

In step S1, as illustrated in FIG. 6 , a growth substrate 400 isprovided (in substep S11), and an epitaxial structure is formed on thegrowth substrate 400. The epitaxial structure includes a first-typesemiconductor layer 411, a MQW active layer 412, a second-typesemiconductor layer 413, and an AlGaAs-based semiconductor layer 414.The AlGaAs-based semiconductor layer 414 is formed on the growthsubstrate 400 and has a thickness of not less than 30 μm (for instance,30 μm to 300 μm, particularly, 30 μm to 50 μm, 50 μm to 100 μm, 100 μmto 150 μm, 150 μm to 300 μm, or other range therewithin). Thesecond-type semiconductor layer 413 is formed on the AlGaAs-basedsemiconductor layer 414 opposite to the growth substrate 400. The activelayer 412 is made from aluminum gallium indium phosphide (AlGaInP) andformed on the second-type semiconductor layer 413 opposite to theAlGaAs-based semiconductor layer 414. The first-type semiconductor layer411 is formed on the active layer 412 opposite to the second-typesemiconductor layer 413.

The term “first-type” refers to being doped with a first conductivitytype dopant, and the term “second-type” refers to being doped with asecond conductivity type dopant that is opposite in conductivity type tothe first conductivity type dopant. For instance, the first conductivitytype dopant may be a p-type dopant, and the second conductivity typedopant may be an n-type dopant, and vice versa.

The growth substrate 400 may be made from gallium arsenide (GaAs) or anyother suitable material.

In substep S12, the AlGaAs-based semiconductor layer 414 is formedthrough liquid phase epitaxy. The thickness of the AlGaAs-basedsemiconductor layer 414 in this embodiment ranges from 50 μm to 220 μm.The AlGaAs-based semiconductor layer 414 may have a content of aluminumwhich ranges from 20 mol % to 95 mol % based on a total molar content ofAlGaAs. For instance, the content of aluminum may be 30 mol % to 70 mol% based on the total molar content of AlGaAs. The content of aluminumdepends on a desired wavelength of light emitted from the flip-chiplight emitting device produced by the method.

In substep S13, the second-type semiconductor layer 413, the activelayer 412, and the first-type semiconductor layer 411 are formed throughMOCVD.

In this embodiment, the first-type semiconductor layer 411 is a p-typesemiconductor layer and has sublayers shown in Table 1 below, and thesecond-type semiconductor layer 413 is an n-type semiconductor layer andhas sublayers shown in Table 1. It should be noted that the sublayer(s)illustrated in Table 1 may be dispensed with in other embodiments,and/or additional sublayer(s) may be provided in other embodiments. Forexample, the n-type window sublayer illustrated in Table 1 may bedispensed with, and/or an n-type barrier sublayer, a p-type barriersublayer, an AlGaInP-based transition sublayer, and so forth may beadditionally provided.

Table 1 also shows the material, thickness, and function regarding thelayers and their sublayers (if any) of the epitaxial structure and thegrowth substrate 400. From the top row to the bottom row of Table 1, thelayers and their sublayers (if any) of the epitaxial structure arelisted in a distal-to-proximal manner toward the growth substrate 400.

P Thickness Material (nm) Function First-type p-type GaP 500 to 5000Current semiconductor window spreading and layer 411 sublayer ohmiccontact p-type AlGaInP 3 to 100 Serving as a transition gradientsublayer interface between AlInP and GaP, and enhancing crystal latticequality of GaP p-type AlInP + 50 to 5000 Providing cladding Mg holessublayer p-type AlInP/ 0* to 1000 Blocking barrier AlGaInP entry of Mgsublayer into the (or spacer active layer layer) 412 to secureperformance MQW active N/A AlGaInP 10 to 20 per Serving to layer 412barrier-well determine the pair (a total wavelength of of 2 to 50 lightemitted barrier-well and luminance pairs) Second-type n-type AlInP/ 0*to 1000 Blocking semiconductor barrier AlGaInP entry of Si layer 413sublayer into the (or spacer active layer sublayer) 412 to secureperformance n-type AlInP + Si 50 to 5000 Providing cladding electronssublayer n-type Al_(c)Ga_(1-c)InP 0* to 6000 Current window spreadingsublayer n-type GaAs 5 to 20 Ohmic contact ohmic contact sublayerAlGaAs-based N/A AlGaAs 50,000 to Supporting semiconductor 220,000 thelayers of layer 414 the epitaxial structure thereabove, and serving as alight exiting layer Growth N/A GaAs Easily Growth of the substrate 400determinable epitaxial in the art structure *a thickness of 0 means thatthe sublayer may be optional.

Regarding the AlGaAs-based semiconductor layer 414, since the crystallattice of the material thereof (AlGaAs) almost completely matches withthat of the material (GaAs) of the n-type ohmic contact sublayer of thesecond-type semiconductor layer 413, liquid phase epitaxy can beconducted for rapid epitaxial growth. Furthermore, the AlGaAs materialdoes not absorb light, such that the AlGaAs-based semiconductor layer414 can serve as a light exiting layer.

The n-type ohmic contact sublayer of the second-type semiconductor layer413 is to be in ohmic contact with an electrode as described later.Since the n-type ohmic contact sublayer is made from GaAs, lightabsorption can be reduced. The n-type ohmic contact sublayer may have athickness of smaller than 50 nm, for example, a thickness ranging from 5to 20 nm. In other embodiments, the n-type ohmic contact sublayer may bemade from other material, such as AlGaAs or AlGaInP.

The n-type window sublayer of the second-type semiconductor layer 413 isformed on the n-type ohmic contact sublayer of the second-typesemiconductor layer 413 mainly for current spreading. Regarding then-type window sublayer, its current spreading ability is correlated withits thickness (the larger its thickness, the better its currentspreading ability). Therefore, the thickness of the n-type windowsublayer can be adjusted based on the thickness of a flip-chip lightemitting device to be produced, and may be smaller than 5000 nm. Forexample, since a flip-chip light emitting device having a length of notgreater than 100 μm normally does not require additional currentspreading, the thickness of the n-type window sublayer may be 0 (namely,the n-type window sublayer may be dispensed with) in such case. Foranother example, when a flip-chip light emitting device having athickness of not smaller than 300 μm is to be produced, the thickness ofthe n-type window sublayer may range from 500 nm to 5000 nm.

The active layer 412 is the light emitting layer of the epitaxialstructure, which determines the wavelength of light emitted andluminance. In this embodiment, the barriers and wells of the activelayer 412 are respectively made from Al_(a1)Ga_(1-a1)InP andAl_(a2)Ga_(1-a2)InP, where a1 is larger than a2.

The materials for the n-type cladding sublayer of the second-typesemiconductor layer 413 and the p-type cladding sublayer of thefirst-type semiconductor layer 411 are selected based on the band gap ofthe active layer 412. For instance, when the active layer 412 isdesigned to emit light having a wavelength of not less than 670 nm andhence to have a lower band gap, the cladding sublayers may be made fromAlGaAs or AlGaInP. For another instance, when the active layer 412 isdesigned to emit light having a wavelength of lower than 670 nm(particularly not greater than 640 nm) and hence to have a larger bandgap (of normally not less than 1.9 eV), the cladding sublayers should bemade from a material having a sufficiently large band gap which isnormally Al_(b)In_(1-b)P (where b is larger than 0 and not greater than0.5). Concerning the active layer 412 which is made from anAlGaInP-based material, the matched material having the largest band gapis Al_(0.0)In_(0.5)P. Accordingly, in this embodiment, the n-typecladding sublayer of the second-type semiconductor layer 413 and thep-type cladding sublayer of the first-type semiconductor layer 411 bothmay be made from Al_(0.5)In_(0.5)P, so that the band gap between theactive layer 412 and the p-type cladding sublayer of the first-typesemiconductor layer 411 can be maximized.

Undoped AlInP or AlGaInP sublayers may be respectively formed on twoopposite sides of the active layer 412. By not introducing a dopant intothese sublayers, diffusion of the p-type and n-type dopants from thefirst-type and second-type semiconductor layers 411, 413 into the activelayer 412 can be prevented, thus securing the performance of the activelayer 412.

The p-type window sublayer of the first-type semiconductor layer 411 isformed on the p-type cladding sublayer of first-type semiconductor layer411 for current spreading. In this embodiment, the p-type windowsublayer may be made from a GaP material and have a thickness of 1.2 μm.However, since the GaP material of the p-type window sublayer and theAlInP material of the p-type cladding sublayer are quite different inlattice constant, an AlGaInP-based transition sublayer is sandwichedbetween the p-type cladding sublayer and the p-type window sublayer,serving as a gradient interface between these two sublayers andenhancing the crystal lattice quality of the p-type window sublayer.

The layers of the epitaxial structure shown in Table 1 are more suitablefor a flip-chip light emitting device including an epitaxial structurewhich is designed to have a size of not smaller than 100 μm×100 μm, inparticular a size of not smaller than 300 μm×300 μm.

In step S2 (illustrated in FIGS. 7 to 10 ), a first electrode 421 and asecond electrode 422 are formed on an electrode placement side of theepitaxial structure facing away from the growth substrate 400, so thatthe first and second electrodes 421, 422 are electrically connected withthe first-type and second-type semiconductor layers 411, 413,respectively (see FIG. 8). In this embodiment, the first and secondelectrodes 421, 422 are p-type and n-type electrodes, respectively. StepS2 is further described in detail below.

First of all, as shown in FIG. 7 , the first-type semiconductor layer411, the active layer 412, and the second-type semiconductor layer 413are partially etched, so that the second-type semiconductor layer 413 ispartially exposed to have an exposed surface A. More specifically, thep-type window sublayer, the p-type transition sublayer, the p-typecladding sublayer, the p-type barrier sublayer, the active layer 412,the n-type barrier sublayer, the n-type cladding sublayer, and then-type window sublayer shown in Table 1 are partially etched, until then-type ohmic contact sublayer shown in Table 1 is partially exposed tohave the exposed surface A. Dry etching may be conducted until then-type window sublayer is partially exposed to have an exposed portion,and wet etching may be subsequently conducted to remove the exposedportion of the n-type window sublayer to partially expose the n-typeohmic contact sublayer. The exposed surface A of the n-type ohmiccontact sublayer is to be in ohmic contact with the second electrode422.

Afterward, as shown in FIG. 8 , the first electrode 421 is formed on aremaining portion of the p-type window sublayer of the first-typesemiconductor layer 411, and the second electrode 422 is formed on theexposed surface A of the n-type ohmic contact sublayer of thesecond-type semiconductor layer 413. The first and second electrodes421, 422 may be made from an Au/AuZn/Au material. In this embodiment,the first and second electrodes 421, 422 are subjected to annealing soas to be in ohmic contact with the epitaxial structure.

Referring to FIG. 9 , a protective insulation layer 440 is formedpartially over the epitaxial structure opposite to the growth substrate400, so that the first and second electrodes 421, 422 are partiallyexposed. The protective insulation layer 440 may be made from siliconoxide, silicon nitride, aluminum oxide, or so forth. The protectiveinsulation layer 440 may have a thickness of not less than 1 μm.

Referring to FIG. 10 , a first metallic layer 431 is formed over thefirst electrode 421 and partially over the protective insulation layer440, so that the first electrode 421 is totally unexposed. Likewise, asecond metallic layer 432 is formed over the second electrode 422 andpartially over the protective insulation layer 440, so that the secondelectrode 422 is totally unexposed. The first and second metallic layers431, 432 serve as extended electrodes respectively for the first andsecond electrodes 421, 422. In addition, the first and second metalliclayers 431, 432 may also serve as reflective mirrors. The first andsecond metallic layers 431, 432 may be made from a metallic materialsuch as titanium, platinum, aluminum, gold, silver, copper, etc.

It should be noted that even though the second electrode 422 is formedon the exposed surface A of the second-type semiconductor layer 413 inthis embodiment, the second electrode 422 may be provided in a differentmanner in other embodiment. For example, instead of forming the largerexposed surface A of the second-type semiconductor layer 413 shown inFIG. 7 , one recess (or more) may be formed to extend through thefirst-type semiconductor layer 411 and the active layer 422, so that asmaller surface of the second-type semiconductor layer 413 is exposed.Therefore, an electrically conductive pillar, which serves to beconnected with the second electrode 422 provided outside the recess, maybe formed in the recess and extend outwardly of the recess to outreachthe first-type semiconductor layer 411. In such case, the secondelectrode 422 may be provided to be flush with the first electrode 421,or may be provided outside the epitaxial structure.

In step S3, as shown in FIG. 11 , the growth substrate 400 is removed toexpose a surface of the AlGaAs-based semiconductor layer 414. After suchremoval, the AlGaAs-based semiconductor layer 414 can support thereonthe rest of the epitaxial structure (i.e. the second-type semiconductorlayer 413, the active layer 412, and the first-type semiconductor layer411) for achieving physical stability, and a first embodiment of theflip-chip light emitting device according to the present disclosure isobtained. During the removal of the growth substrate 400, theAlGaAs-based semiconductor layer 414 can be used to support the growthsubstrate 400.

The removal of the growth substrate 400 can be conducted using variousmethods depending on the material of the growth substrate 400. Exemplarysuitable methods include, but are not limited to, laser lift-off (LLO),grinding, and etching. Since the growth substrate 400 is made from GaAsin this embodiment, etching or grinding may be applied to conduct theremoval of the growth substrate 400. Considering etching, selectiveetching with an etch stop layer may be applied to control and stopetching.

A second embodiment of the flip-chip light emitting device and theproduction method thereof is generally similar to the first embodiment.In particular, the layers and their sublayers (if any) of the epitaxialstructure and the growth substrate 400 in the second embodiment aregenerally similar to those shown in Table 1. However, the differencesbetween the second and first embodiments are described below.

In the second embodiment, the second-type semiconductor layer 413 doesnot have the n-type ohmic contact sublayer, and the n-type windowsublayer of the second-type semiconductor layer 413, in addition to itscurrent spreading function, serves to be in ohmic contact with thesecond electrode 422. Besides, the n-type window sublayer has athickness ranging from 20 nm to 6000 nm.

Since the n-type window sublayer serves as an ohmic contact sublayer, instep S2, the second-type semiconductor layer 413 is only required to beetched (e.g. through drying etching) to partially expose the n-typewindow sublayer, so that the n-type window sublayer has the exposedsurface A (for the second electrode 422 to be formed thereon).Therefore, the simplification of the etching process may improve theproduction yield. In addition, in the second embodiment, the omission ofthe n-type ohmic contact sublayer shown in Table 1 can improve the lightemitting efficiency since light can pass through the epitaxial structuremore easily.

After formation of the second electrode 422 on the n-type windowsublayer, high-temperature annealing may be conducted at, for example, atemperature of not less than 300° C., so that the metal atoms in thesecond electrode 422 diffuses into the n-type window sublayer for thesecond electrode 422 and the n-type window sublayer to be in ohmiccontact.

The second electrode 422 may be made from a material selected from thegroup consisting of gold, germanium, nickel, and combinations thereof(e.g. alloys thereof). Examples of the aforesaid combinations include,but are not limited to, AuGe, AuGeNi, Au/AuGe/Ni/Au, and Au/AuGeNi/Au.In addition, the second electrode 422 may have a multi-layeredstructure, and may have a layer that is in contact with the n-typewindow sublayer, that may be made from Au or an Au-containing alloy, andthat may have a thickness ranging from 1 nm to 50 nm (e.g. 5 to 20 nm).

Regarding the Al_(c)Ga_(1-c)InP material of the n-type window sublayer,c may range from 0.5 to 1, so that the undesired light absorption of then-type window sublayer can be reduced. Further, in order to achievebetter lattice matching between the aluminum gallium indium phosphidematerial and the material (e.g. gallium arsenide) of the growthsubstrate 400 for accomplishing more satisfactory crystal growth of thealuminum gallium indium phosphide material, c may range from 0.6 to 0.8.

For achieving better horizontal current spreading, the thickness of then-type window sublayer may range from 2.5 μm to 3.5 μm (i.e. 2500 nm to3500 nm).

Based on the desired ohmic contact effect and current spreading effect,the n-type window sublayer may have a doping concentration of not lessthan 1×10¹⁸ atoms/cm³ (e.g., 1×10¹⁸ atoms/cm³ to 2×10¹⁸ atoms/cm³). Alower doping concentration may lead to a higher ohmic contactresistance. A higher doping concentration may lead to light absorptionand hence reduce the light emitting efficiency. The doping concentrationof the n-type window sublayer in the thickness direction of the n-typewindow sublayer may be uniform or not. In the case of non-uniformity,the doping concentration of the n-type window sublayer may vary in thethickness direction of the n-type window sublayer. Namely, the closer tothe second electrode 422, the higher the doping concentration of then-type window sublayer can be for improving the ohmic contact.

The second embodiment of the flip-chip light emitting device is suitableto have a small size. For instance, the epitaxial structure of theflip-chip light emitting device may have a size of not greater than 300μm×300 μm, so that the flip-chip light emitting device can be a miniflip-chip light emitting device. Alternatively, the flip-chip lightemitting device may be a micro flip-chip light emitting device.

A third embodiment of the flip-chip light emitting device and theproduction method thereof is generally similar to the first embodiment.In particular, the layers and their sublayers (if any) of the epitaxialstructure and the growth substrate 400 in the third embodiment aregenerally similar to those shown in Table 1. However, the differencesbetween the third and first embodiments are described as follows.

The n-type window sublayer of the second-type semiconductor layer 413 ismade from Al_(d)Ga_(1-d)As instead. Regarding such Al_(d)Ga_(1-d)Asmaterial, d may range from 0.45 to 0.65 (e.g. d may be 0.5). Compared tothe AlGaInP-based window sublayer, the limit of the growth rate of theAlGaAs-based window sublayer can be increased from 7 Å/S to 40 Å/S(namely, the growth rate can be enhanced by at least threefold). Thus,the growth time of the epitaxial structure can be reduced by at least30%. Since the production time can be greatly reduced, the productioncost can be lowered as well, facilitating mass production. Besides, dueto the higher growth temperature window (680±30° C.) of theAl_(d)Ga_(1-d)As material, the growth of the epitaxial structure can bemore easily controlled.

A fourth embodiment of the flip-chip light emitting device and theproduction method thereof is generally similar to the first embodiment.In particular, the layers and their sublayers (if any) of the epitaxialstructure and the growth substrate 400 in the fourth embodiment aregenerally similar to those shown in Table 1. However, the differencesbetween the fourth and first embodiments are described below.

In the fourth embodiment, the second-type semiconductor layer 413 doesnot have the n-type window sublayer.

Moreover, the fourth embodiment of the flip-chip light emitting deviceis suitable to have a small size. For instance, the epitaxial structureof the flip-chip light emitting device may have a size of not largerthan 300 μm×300 μm, so that the flip-chip light emitting device can be amini flip-chip light emitting device. Alternatively, the flip-chip lightemitting device may be a micro flip-chip light emitting device.

A fifth embodiment of the flip-chip light emitting device and theproduction method thereof is generally similar to the first embodiment.In particular, the layers and their sublayers (if any) of the epitaxialstructure and the growth substrate 400 in the fifth embodiment aregenerally similar to those shown in Table 1. However, the differencesbetween the fifth and first embodiments are described as follows.

The AlGaAs-based semiconductor layer 414 is n-type doped, and has athickness ranging from 30 μm to 100 μm.

Furthermore, referring to FIG. 12 , the second electrode 422 is formedon the AlGaAs-based semiconductor layer 414 instead. In other words, instep S2, the first-type semiconductor layer 411, the active layer 412,the second-type semiconductor layer 413, and the AlGaAs-basedsemiconductor layer 414 are partially etched, so that the AlGaAs-basedsemiconductor layer 414 is partially exposed to have the exposed surfaceA for the second electrode 422 to be formed thereon. Therefore, theAlGaAs-based semiconductor layer 414 serves to be in ohmic contact withthe second electrode 422, and the second-type semiconductor layer 413does not have the n-type window sublayer and the n-type ohmic contactsublayer.

Accordingly, the fifth embodiment of the flip-chip light emitting deviceis suitable to have a small size. For instance, the epitaxial structureof the flip-chip light emitting device may have a size of not largerthan 300 μm×300 μm, so that the flip-chip light emitting device can be amini flip-chip light emitting device. Alternatively, the flip-chip lightemitting device may be a micro flip-chip light emitting device.

A sixth embodiment of the flip-chip light emitting device and theproduction method thereof is generally similar to the first embodiment.In particular, the layers and their sublayers (if any) of the epitaxialstructure and the growth substrate 400 in the sixth embodiment aregenerally similar to those shown in Table 1. However, the differencesbetween the fifth and first embodiments are described as follows.

The first-type semiconductor layer 411 is an n-type semiconductor layerinstead, and the second-type semiconductor layer 413 is a p-typesemiconductor layer instead. Specifically, the window sublayer, thecladding sublayer, and the barrier sublayer of the first-typesemiconductor layer 411 are of n-type instead, and hence such n-typecladding sublayer (made from AlInP+Si) and such n-type barrier sublayerrespectively function to provide electrons and block entry of Si intothe active layer 412 for securing performance. Likewise, the windowsublayer, the cladding sublayer, and the barrier sublayer of thesecond-type semiconductor layer 413 are of p-type, and hence such p-typecladding sublayer (made from AlInP+Mg) and such p-type barrier sublayerrespectively function to provide holes and block entry of Mg into theactive layer 412 for securing performance. Due to the aforesaid dopingtype of the first-type and second-type semiconductor layers 411, 413,the first and second electrodes 421, 422 are of n-type and p-type,respectively.

Furthermore, the first-type semiconductor layer 411 does not have thetransition sublayer, and the second-type semiconductor layer 413 doesnot have the ohmic contact sublayer (thus, the p-type window sublayer ofthe second-type semiconductor layer 413, in addition to its currentspreading function, serves to be in ohmic contact with the secondelectrode 422). The p-type window sublayer of the second-typesemiconductor layer 413 has a thickness ranging from 20 nm to 6000 nm.

Despite above, in a variation of the sixth embodiment, the second-typesemiconductor layer 413 may have the ohmic contact sublayer (of p-typein such case), and the ohmic contact sublayer functions to be in ohmiccontact with the second electrode 422. In another variation of the sixthembodiment, the second-type semiconductor layer 413 does not have thewindow sublayer and the ohmic contact subslayer, and the AlGaAs-basedsemiconductor layer 414 is of p-type and serves to be in ohmic contactwith the second electrode 422 like that in the fifth embodiment.

The advantages of the flip-chip light emitting device and the productionmethod thereof according to the present disclosure reside in thefollowing.

First, since the AlGaAs-based semiconductor layer 414 is made from anAlGaAs material (e.g. Al_(x)Ga_(1-x)As), the AlGaAs-based semiconductorlayer 414 can be grown in a more efficient manner, thereby improving thegrowth efficiency of the epitaxial structure and reducing the productioncost. Moreover, due to its AlGaAs material, the AlGaAs-basedsemiconductor layer 414 can enhance the performance of the flip-chiplight emitting device, and can serve as a satisfactory light exitinglayer.

Secondly, the AlGaAs-based semiconductor layer 414 has a thickness ofnot less than 30 μm, such that the AlGaAs-based semiconductor layer 414can serve as a support layer for supporting the growth substrate 400during removal thereof. Therefore, a bonding process is not required forthe growth substrate 400 to be removed, improving the production yieldof the flip-chip light emitting device.

In the description above, for the purposes of explanation, numerousspecific details have been set forth in order to provide a thoroughunderstanding of the embodiments. It will be apparent, however, to oneskilled in the art, that one or more other embodiments may be practicedwithout some of these specific details. It should also be appreciatedthat reference throughout this specification to “one embodiment,” “anembodiment,” an embodiment with an indication of an ordinal number andso forth means that a particular feature, structure, or characteristicmay be included in the practice of the disclosure. It should be furtherappreciated that in the description, various features are sometimesgrouped together in a single embodiment, figure, or description thereoffor the purpose of streamlining the disclosure and aiding in theunderstanding of various inventive aspects, and that one or morefeatures or specific details from one embodiment may be practicedtogether with one or more features or specific details from anotherembodiment, where appropriate, in the practice of the disclosure.

While the disclosure has been described in connection with what areconsidered the exemplary embodiments, it is understood that thisdisclosure is not limited to the disclosed embodiments but is intendedto cover various arrangements included within the spirit and scope ofthe broadest interpretation so as to encompass all such modificationsand equivalent arrangements.

What is claimed is:
 1. A light emitting device comprising: an epitaxialstructure including a first-type semiconductor layer, an active layer,and a second-type semiconductor layer, said second-type semiconductorlayer having a second-type cladding sublayer and a second-type windowsublayer, said active layer being made from aluminum gallium indiumphosphide (AlGaInP) and disposed on said second-type semiconductorlayer, said first-type semiconductor layer being disposed on said activelayer opposite to said second-type semiconductor layer; a firstelectrode disposed on an electrode placement side of said epitaxialstructure, so that said first electrode is electrically connected withsaid first-type semiconductor layer; and a second electrode disposed onsaid electrode placement side of said epitaxial structure, so that saidsecond electrode is electrically connected with said second-typesemiconductor layer, said second electrode being in ohmic contact withsaid second-type window sublayer.
 2. The light emitting device asclaimed in claim 1, wherein said first-type semiconductor layer is madefrom a material selected from the group consisting of AlGaAs, AlGaInP,aluminum indium phosphide (AlInP), gallium phosphide (GaP), andcombinations thereof.
 3. The light emitting device as claimed in claim1, wherein said second-type semiconductor layer is made from a materialselected from the group consisting of AlGaAs, AlGaInP, AlInP, GaP, andcombinations thereof.
 4. The light emitting device as claimed in claim1, wherein said second-type cladding sublayer and said second-typewindow sublayer that are proximate to and distal from said active layer,respectively, said second-type window sublayer being made from amaterial selected from the group consisting of AlGaAs, AlGaInP, and acombination thereof.
 5. The light emitting device as claimed in claim 1,wherein said second electrode is in one of a single-layered form and amulti-layered form, a contact portion of said second electrode incontact with said second-type window sublayer being made from one ofgold (Au) and an Au-containing alloy.
 6. The light emitting device asclaimed in claim 5, wherein said contact portion of said secondelectrode has a thickness ranging from 5 nm to 20 nm.
 7. The lightemitting device as claimed in claim 1, wherein said epitaxial structurehas a size of not larger than 300 μm×300 μm, said second-type claddingsublayer and said second-type window sublayer that are proximate to anddistal from said active layer, respectively.
 8. The light emittingdevice as claimed in claim 1, wherein said first-type semiconductorlayer has a first-type window sublayer and a first-type claddingsublayer that are distal from and proximate to said active layer,respectively.
 9. The light emitting device as claimed in claim 1,further comprising a first metallic layer that is disposed over and incontact with said first electrode, and a second metallic layer that isdisposed over and in contact with said second electrode, said first andsecond metallic layers being larger in surface area than said first andsecond electrodes, respectively.
 10. The light emitting device asclaimed in claim 9, wherein said first and second metallic layers arereflective layers.
 11. The light emitting device as claimed in claim 1,wherein said second-type window sublayer has a doping concentration notless than 1×10¹⁸ atoms/cm³.
 12. The light emitting device as claimed inclaim 1, wherein said second-type window sublayer has a dopingconcentration ranging from 1×10¹⁸ atoms/cm³ to 2×10¹⁸ atoms/cm³.
 13. Thelight emitting device as claimed in claim 1, wherein said second-typewindow sublayer has a doping concentration varying in a thicknessdirection thereof.
 14. The light emitting device as claimed in claim 1,wherein said second-type window sublayer has a thickness ranging from2.5 μm to 3.5 μm.
 15. The light emitting device as claimed in claim 1,wherein some metal atoms in the second electrode diffuses into thesecond-type window sublayer.
 16. A light emitting apparatus comprisingat least one light emitting device as claimed in claim
 1. 17. The lightemitting apparatus as claimed in claim 16, wherein said epitaxialstructure of said light emitting device has a size of not larger than300 μm×300 μm, said second-type cladding sublayer and said second-typewindow sublayer that are proximate to and distal from said active layerof said epitaxial structure, respectively.
 18. The light emittingapparatus as claimed in claim 16, wherein said epitaxial structure ofsaid light emitting device has a size of not larger than 300 μm×300 μm.19. The light emitting apparatus as claimed in claim 16, wherein saidsecond-type semiconductor layer of said epitaxial structure furtherincludes a second-type barrier sublayer disposed on said second-typecladding sublayer opposite to said second-type window sublayer.
 20. Thelight emitting apparatus as claimed in claim 14, wherein saidsecond-type window sublayer has a doping concentration not less than1×10¹⁸ atoms/cm³.